The purpose of this study is to investigate relationships between differential participation in a preschool-to-Grade 3 early childhood intervention program and adolescent adjustment outcomes for economically disadvantaged children at risk of school failure. These outcomes include social adjustment, delinquency, cognitive school achievement, retention in grade, special education placement, and school dropout (Grades 9 to 12). Three major questions are addressed: (a) Is the duration of early childhood intervention associated with adolescent adjustment outcomes over time? (b) What are the effects of participation in extended childhood intervention up to Grade 3 relative to participation in preschool and kindergarten intervention and other intervention? (c) What are the mechanisms through which intervention effects are transmitted to adjustment outcomes? Answers to these question are necessary for several reasons. First, the effects of preschool intervention followed by educational support in the early primary grades are largely unknown. Most of the evidence on intervention effectiveness comes from researcher- initiated model programs that differ in significant ways from government- initiated programs implemented in inner cities. Second, the general lack of longitudinal studies from early childhood to adolescence limits knowledge on the effects of intervention programs during transitional periods, such as adolescence. Finally, about one-quarter of children under the age of six live in poverty and this number appears to be increasing. Unless effective early intervention programs are developed and tested, social and school difficulties may increase as well. Through expanding an existing longitudinal data base on children and their families -- The Longitudinal Study of Children at Risk -- the proposed investigation will comprehensively evaluate the effects of the extended intervention (Child Parent Center and Expansion Program) by surveying children, parents, and teachers, by obtaining comprehensive school records (i.e., achievement test scores, delinquency information, and school status), and by interviewing a subsample of children. Because children varied substantially in the timing and duration of experience, seven intervention and comparison groups will be formed to determine effectiveness. Data will be linked to the extensive longitudinal data base. This study will provide rare longitudinal evidence on the effectiveness of Head Start-type extended childhood interventions across a wide range of outcomes. The long-term goals of the study are (a) to increase knowledge concerning the optimal timing and duration of early childhood intervention programs, (b) to identify the mechanisms through which intervention during early childhood may be transmitted over time, and (c) to enhance theoretical understanding of the role of intervention programs from early childhood to adolescence.